Detectives investigating a fire in which six children died have arrested the children's parents on suspicion of murder.

The Derbyshire force confirmed that a 55-year-old man and a 31-year-old woman, who are from Derby, were arrested on Tuesday morning. They have not been identified by police but it is thought they are Mick Philpott and his wife Mairead.

At a press conference on Tuesday the force's assistant chief constable, Steve Cotterill, said a couple had been arrested at 10am in Derby city centre. They are being questioned on suspicion of murder.

A fierce fire broke out at the house in Allenton in the early hours of Friday 11 May, resulting in the deaths of six children.

The victims were Duwayne Philpott, 13, who died of his injuries in hospital; Jade Philpott, 10, and brothers John Philpott, nine, Jack Philpott, seven, Jessie Philpott, six, and Jayden Philpott, five.

The assistant chief constable urged people with information to get in touch, saying: "Please do the right thing for the six children who died in the fire. The latest arrests are just one step further in the investigation. It is absolutely vital that if you know anything you think could help us, come forward now, do not wait any longer.

"What we need to do now is carefully take our time, question the two individuals concerned and piece it together with everything else we know to date."

Earlier Cotterill said: "I suspect there may still be people with crucial information who have not yet come forward to speak to us."

He gave them a "personal reassurance" that police would deal with their information sensitively.

The officer emphasised that the investigation was still ongoing and would be a lengthy process as it was a complex inquiry. Other people have been arrested and subsequently released on bail.

Police have again increased their presence on Victory Road at the scene of the fire. The mobile police station will return and there will be extra patrols in the area. The front door, where petrol was apparently poured, has been replaced. Floral tributes will be taken away by police and placed in a nearby church.

At a press conference five days after the fire, on 16 May, Mick Philpott spoke of his anguish and said he and his wife had been overwhelmed with support from the local community.

Philpott revealed that the couple had donated Duwayne's organs to another child, which "took away" some of their pain. The couple said they had been overwhelmed by the response of the community.

A 28-year-old woman and a 38-year-old man, both from Derby, were arrested by officers investigating the deaths, but were subsequently released without charge.

The children were asleep in their beds upstairs when the fire broke out at the semi-detached property in the early hours.

Police have removed two vehicles from the couple's home including a caravan and van for forensic examination. A uniformed officer is standing guard outside the property, which is taped off.

Cotterill said he appreciated the case had deeply affected the local community and residents wanted answers as to what had happened and why. He urged them to be patient "and to continue to show the excellent support they have given us to date".

Anyone with information was urged to contact the police on 101 or Crimestoppers on 0800 555 111